KR960008117B1 - Polyolefin-vegetable fibre moulding resin composition - Google Patents

Abstract

The resin composition is usable as a resin composition of low production cost and exhibits excellent mechanical properties in tensile strength and impact strength. The resin composition is prepared by the steps of: (A) subjecting said vegetable fiber to a surface treatment by using a isocyanate system compound, so as to further improve the distribution and dispersion properties thereof; (B) adding thereto a small amount of denatured-polyolefin and other additives, e. g., anti-oxidants, lubricants and waxes; (C) finally preparing a molding by employing a commonly used method.

Description

Resin composition for polyolefin-plant fiber type molding

The present invention relates to a resin composition for polyolefin-plant fiber based molding suitable for molding processing, such as extrusion molding or injection molding. In more detail, the present invention is mainly made of polyolefin and plant fibers, wherein the plant fibers are plant fibers treated with a surface treatment agent, such resin composition is suitable for molding industrial materials and the like.

Plant fibers such as wood flour, rice hull, and cotton have not only suitable requirements for materials requiring various mechanical strengths, electrical properties, and moldability, but also are inexpensive and rich in raw materials. It is widely used. However, unlike plant fiber, which is widely used as a filler for thermosetting resins, polyolefin is used as a filler.

Molded products obtained from polyolefins have excellent physical properties, but the disadvantages of the mechanical rigidity is pointed out, and in order to solve these defects, a method of melt-mixing plant fibers such as wood flour, chaff, cotton, etc. into polyolefins has been attempted. However, the molded article thus obtained has the drawback that the rigidity is improved, but mechanical properties such as tensile strength and impact resistance, which are important physical properties of the plastic molded article, are significantly lower than those of the molded article made of pulley olefin alone.

The moldings obtained by adding plant fibers to polyolefins have such drawbacks because vegetable oils are not melted at the melting temperature of the polyolefins and are difficult to uniformly disperse in the molten polyolefins. Accordingly, it has been a very difficult problem to prepare a resin composition for molding polyolefin-plant fiber based resin having excellent mechanical properties such as rigidity, tensile strength and impact resistance.

As described above, methods for solving the shortcomings of the resin composition for molding processing consisting of polyolefin and plant fibers have been continuously proposed. In Japanese Patent Laid-Open No. 58-56581, the addition of rosin-based materials, petroleum resins, plasticizers, synthetic rubbers or inorganic fillers to polyolefin-plant fiber compositions improves the dispersibility of plant fibers and improves the mechanical properties of the moldings. It is shown to be. However, according to the above-described method, since various materials such as rosin-based materials, petroleum resins, plasticizers, synthetic rubbers, and inorganic fillers are used in addition to polyolefins and plant fibers, the manufacturing process of the molded products is complicated, and the cost of the molded products is increased. There is this.

In order to improve the shortcomings of the polyolefin-plant fiber composition, a method of exchanging polyolefins with maleic anhydride-modified polyolefins has also been proposed. In order to solve the problem of the above price, Japanese Patent Laid-Open No. 63-230750 discloses a composition in which 40 to 60 parts by weight of plant fibers are mixed with a mixed resin having a weight ratio of polyolefin and modified polyolefin of 97/3 to 60/40. Suggesting. However, when the mixed amount of the modified polyolefin is small, mechanical properties such as tensile strength and impact strength are lowered. When the mixed amount of the modified polyolefin is large, there is a drawback that the price of the composition or the molded product whose mechanical properties are improved is increased.

SUMMARY OF THE INVENTION An object of the present invention is to provide a resin composition having excellent mechanical properties such as stiffness, tensile strength and cost competitiveness by solving various problems of the resin composition for forming a polyolefin-plant fiber system.

The present inventors have surface treated plant fibers using isocyanate compounds to improve the dispersibility and distribution of the plant fibers in the resin and improve the mechanical properties of the moldings in the preparation of the polyolefin-plant fiber composition, and a small amount of modified polyolefin is added thereto. And other additives such as antioxidants, lubricants, and waxes to the polyolefin base resin, and then the molded article is manufactured in a conventional manner. As a result, the mechanical properties such as stiffness, tensile strength and impact strength are excellent, and the molded article is manufactured. The inventors have invented a polyolefin-plant fiber resin composition capable of producing an inexpensive resin composition. That is, the resin composition for polyolefin-plant fiber molding of the present invention contains 40 to 90 parts by weight of polyolefin component and 60 to 10 parts by weight of plant fiber surface-treated with an isocyanate compound, and 0.5 to 20 parts by weight of modified polyolefin This addition was characterized.

In the polyolefin-plant fiber molding composition, the isocyanate compound used as the surface treatment agent in the present invention is present on the surface of the plant fiber to improve the dispersibility and distribution of the plant fiber to the resin and to obtain a molded product having excellent mechanical properties. It inhibits decomposition of plant fiber during high temperature kneading with resin, and acts as a lubricating agent to reduce breakage and increase dispersibility of plant fiber during kneading, and also adheres at the interface between plant fiber and base resin. It improves the mechanical properties and increases the mechanical properties.

In addition, the modified polyolefin used in the present invention is present at the interface between the non-modified polyolefin and the plant fiber in the polyolefin-plant fiber composition to act as a compatibilizer to increase interfacial adhesion, and also to improve the melt dispersion state of the plant fiber. It works to improve.

Hereinafter, the present invention will be described in detail.

The composition of the present invention contains 40 to 90 parts by weight of polyolefin component and 60 to 10 parts by weight of plant fiber surface-treated with an isocyanate compound.

Suitable surface treating agents of the present invention are isocyanate compounds. Examples thereof include paraphenylene diisocyanate, 2-chloro-1, 4-phenyl diisocyanate, 2, 4-toluene diisocyanate, 1, 5-naphthalene diisocyanate, hexamethylene diisocyanate, and the like. Since the surface treatment agent does not require a pretreatment step, such as a Henschel mixer, the surface treatment agent is added simultaneously with the surface of the plant fiber without performing any pretreatment, or the surface treatment agent or the isocyanate compound has no reactivity with the polyolefin resin, and thus, polyolefin, plant fiber and other additives. It may be added simultaneously with the surface treatment, the amount of use is preferably 0.5 to 20 parts by weight to 100 parts by weight of plant fibers. If the amount is less than 0.5 parts by weight, the surface treatment effect is insignificant, and if it is more than 20 parts by weight, economic efficiency is reduced.

Base resins useful in the present invention include olefin-based polyolefin resins such as low density polyethylene, medium density, polyethylene, high density polyethylene, polypropylene, ethylene or polymers of propylene and other copolymerizable monomers.

In addition, the plant fiber suitable for the present invention is preferably 40-300 mesh size wood flour, chaff and cotton. When the size of the plant fiber is larger than 40 mesh, the mechanical properties are likely to decrease. When the size of the plant fiber is smaller than 300 mesh, the mechanical properties are excellent, but the manufacturing cost of the plant fiber is increased.

As an additive used in the present invention, the antioxidant is 4,4'-thiobis (2-t-butyl-5-methylphenol), pentaerythryl-tetrakis- [3- (3, 5-di-t -Butyl-4-hydroxyphenyl) -propionate], 2, 2'-methylenebis [4-methyl-6- (1'-methylcyclohexyl) phenol] and tris (2, 4-t-butylphenyl ) Phosphite and the like, the amount of the additive is 0.05 to 1.0 parts by weight, preferably 0.1 to 0.3 parts by weight based on 100 parts by weight of the base resin.

The modified polyolefin used in the present invention is a polyolefin resin modified with maleic anhydride or glycidyl methacrylate or hydroxyethyl methacrylate.

In addition to the above composition, the present invention may add a small amount of a thermal stabilizer, an ultraviolet stabilizer, a lubricant, and the like, and if necessary, a flame retardant or a flame retardant aid may be added.

In order to obtain such a resin composition, plant fibers and other additives surface-treated with a polyolefin resin and an isocyanate compound are kneaded using a kneader to prepare pellets. As the kneader, a balm mixer, a uniaxial kneader, a biaxial kneader, a co-kneader and the like can be used.

In order to prevent pyrolysis of plant fibers during kneading, it is necessary to lower the screw rotation speed of the kneader, make the inner shape of the extrusion die streamlined, and increase the thickness of the extruded strand.

Even in the pellets manufactured as described above, in order to prevent thermal decomposition of the plant fiber during extrusion molding or injection molding, the screw rotation speed of the molding machine is reduced, and in the case of injection molding, the injection pressure and injection speed are decreased, and the hole size of the nozzle is increased and the mold is increased. Care must be taken in the design of the screws, runners and gates.

The resin composition for molding polyolefin-plant fiber system of the present invention has the effect of obtaining a molding resin which is economical and has excellent mechanical properties.

Hereinafter, the embodiment of the present invention will be described in detail. However, the present invention is not limited by these examples.

Example 1

1 part by weight of polyisocyanate (Kumho Mitsui Dotsutsu, MDI-CR200) on a surface of 150 mesh wood flour (CELLULOSIN) is uniformly surface treated for 5 minutes using a 1000 RPM Henschel mixer at 50 ° C.

Polypropylene (Samsung General Chemical Co., Ltd., BJ800) 1 part by weight of maleic anhydride modified polypropylene (EXXELOR, EXXELOR) and antioxidant 4, 4'-thiobis (2-t-butyl-5-methylphenol) , Pentaerythryl-tetrakis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate], 2, 2'-methylenebis [4-methyl-6- ( 1'-methylcyclohexyl) phenyl] and tris (2,4-t-butylphenyl) phosphite 4-4 'were each added 0.1 part by weight, and then mixed uniformly for 5 minutes using a hexel mixer at 50 ° C and 1000 RPM. do.

Subsequently, according to the method described above, 60 parts by weight of the mixed polypropylene resin (A) and 40 parts by weight of the surface-treated wood powder (B) were injected into the primary hopper using a twin screw kneader and the wood powder was injected into the second half hopper. After kneading to prepare a pellet by a conventional method. At this time, the size of the pellet is cut into 2 ~ 5mm, length 3 ~ 7mm. After the pellets were dried for several hours by a conventional method at a temperature of 120 ° C. or higher, the specimens were injection molded at a mold temperature of 50 ° C. and a cylinder temperature of 170 ° C. to 210 ° C. to obtain rigidity (flexural modulus), tensile strength, and Izod impact strength. Measure

All the above properties were measured according to the ASTM test method. The results are shown in Table 1.

Example 2

In Example 1, wood powder surface-treated with 0.5 parts by weight of polyisocyanate is used, and the rest is the same as in Example 1. The results are shown in Table 1.

Example 3

In Example 1, 3 parts by weight of maleic anhydride-modified polypropylene was used, and the rest was the same as in Example 1. The results are shown in Table 1.

Example 4

In Example 2 0.5 parts by weight of maleic anhydride modified polypropylene was used, and the rest thereof were the same as in Example 2. The results are shown in Table 1.

Comparative Example 1

Example 1 uses wood powder not surface-treated with polyisocyanate and the rest is the same as Example 1. The results are shown in Table 1.

Comparative Example 2

In Example 1, maleic anhydride-modified polypropylene was not used, and the rest was the same as in Example 1. The results are shown in Table 1.

Comparative Example 3

In Example 1, wood powder without surface treatment was used, and 10 parts by weight of maleic anhydride modified polypropylene was used. The rest is the same as in Example 1. The results are shown in Table 1.

[Comparative Example 4]

Untreated surface wood powder was used in Example 1 and no maleic anhydride modified polypropylene was used. The rest is the same as in Example 1. The results are shown in Table 1.

Claims (4)

A resin composition for molding polyolefin-plant fiber, comprising 40 to 90 parts by weight of polyolefin resin, 60 to 10 parts by weight of plant fiber surface-treated with an isocyanate compound, and 0.5 to 20 parts by weight of modified polyolefin. The resin composition for polyolefin-plant fiber type molding according to claim 1, wherein the polyolefin resin is polypropylene or polyethylene, and the modified polyolefin is maleic anhydride-modified polypropylene. The resin composition for forming a polyolefin-plant fiber system according to claim 1, wherein the plant fibers are surface-treated with 0.5 to 20 parts by weight of isocyanate compounds based on 100 parts by weight of plant fibers. The resin composition according to claim 1, wherein the plant fibers are wood flour or chaff or cotton of about 40 to 300 mesh.